Induction heating device, induction heating method, and program

Abstract

The purpose of the present invention is to minimize switching losses of an inverter. An induction heating device includes: a plurality of induction heating coils ( 20 ) which are disposed adjacent with each other; a plurality of inverters ( 30 ), each of which has a capacitor ( 40 ) serially connected to each of the induction heating coils ( 20 ), and converts a DC voltage into a square wave voltage; and a control circuit ( 15 ) which controls so as to align the phase of coil currents flowing though the plurality of the induction heating coils ( 20 ), wherein the control circuit ( 15 ) controls the timing at which the square wave voltage transitions such that an instantaneous value of the square wave voltage is preserved in either the DC voltage or a turnover voltage, when the coil current zero crosses.

What is claimed is: 
     
       1. An induction heating device comprising:
 a plurality of induction heating coils which are disposed adjacent to each other; 
 capacitors each of which is connected in series to each of the induction heating coils; 
 a plurality of inverters each of which applies a high frequency voltage converted from a DC voltage to a series circuit of each of the induction heating coils and each of the capacitors; and 
 a control circuit which performs a pulse width control of the high frequency voltage, as well as controls the plurality of the inverters so as to align phases of coil currents flowing through the plurality of the induction heating coils, respectively, 
 wherein the control circuit is configured to vary the amplitude of the coil current by changing a control angle of the coil current, and 
 wherein the DC voltage is common for the plurality of the inverters, and is decreased so that a maximum pulse width of all of high frequency voltages converted by the plurality of the inverters becomes equal to or greater than a predetermined value. 
 
     
     
       2. The induction heating device, according to  claim 1 ,
 wherein the DC voltage is controlled such that a zero-cross timing at which a coil current flowing through the series circuit zero crosses from negative to positive is behind relative to a rising timing of a voltage applied to the series circuit. 
 
     
     
       3. The induction heating device, according to  claim 1 ,
 wherein each of the plurality of the inverters comprises arms, each arm having a transistor, and a diode in a reverse parallel connection, and 
 the DC voltage is generated by a chopper circuit or a converter. 
 
     
     
       4. The induction heating device, according to  claim 1 ,
 further comprising an abnormal stop unit, which stops the plurality of the inverters when there is any inverter in which the high frequency voltage rises after a coil current zero-crosses from negative to positive. 
 
     
     
       5. The induction heating device, according to  claim 1 ,
 wherein the plurality of the induction heating coils are disposed in proximity to a common heating element and 
 the control circuit variably controls a pulse width of a square wave voltage as each of the high frequency voltages so that electromagnetic energies supplied to the heating element by each of the induction heating coils are uniformed. 
 
     
     
       6. An induction heating method for use in an induction heating device including a plurality of induction heating coils which are disposed adjacent to each other, capacitors each of which is connected in series to each of the induction heating coils, and a plurality of inverters each of which applies a high frequency voltage converted from a DC voltage to a series circuit of each of the plurality of the induction heating coils and each of the capacitors, the method comprising:
 performing a pulse width control of the high frequency voltage, 
 controlling the plurality of the inverters, each having the DC voltage in common, so as to align phases of coil currents flowing through the plurality of the induction heating coils, respectively, 
 varying the amplitude of the coil current by changing a control angle of the coil current, and 
 decreasing the DC voltage so that a maximum pulse width of all of high frequency voltages converted by the plurality of the inverters becomes equal to or greater than a predetermined value. 
 
     
     
       7. The induction heating method, according to  claim 6 ,
 wherein the DC voltage is controlled such that a zero-cross timing of a current flowing through the series circuit is behind relative to a rising timing of a voltage applied to the series circuit. 
 
     
     
       8. A computer program, embodied on a computer-readable non-transitory medium, wherein the computer program is configured to execute a method for use in an induction heating device including a plurality of induction heating coils which are disposed adjacent to each other, capacitors each of which is connected in series to each of the induction heating coils, and a plurality of inverters each of which applies a high frequency voltage converted from a DC voltage to a series circuit of each of the plurality of the induction heating coils and each of the capacitors, the method comprising:
 performing a pulse width control of the high frequency voltage, 
 controlling the plurality of the inverters, each having the DC voltage in common, so as to align phases of coil currents flowing through the plurality of the induction heating coils, respectively, 
 varying the amplitude of the coil current by changing a control angle of the coil current, and 
 decreasing the DC voltage so that a maximum pulse width of all of high frequency voltages converted by the plurality of the inverters becomes equal to or greater than a predetermined value.